<!DOCTYPE html>
<html lang='en'>
<head>
    <meta charset='UTF-8'>
    <title>下文规则 3 - 1</title>
</head>
<body>
    <script>
        let arr = ['a', 'b', 'c', function () {
            console.log(this[0]);
        }];
        arr[3]();  // 'a'；数组中枚举出函数进行调用，适用规则 3
    </script>
</body>
</html>
